The invention generally relates to oscillating-piston machines.
Oscillating-piston machines, and in particular an oscillating-piston machine in accordance with the present invention, can be used as internal combustion engines, as pumps or as compressors. An oscillating-piston machine in accordance with the present invention is preferably used as an internal combustion engine and is described in this form in the present description.
If an oscillating-piston machine is used as an internal combustion engine, the individual working strokes of intake, compression, ignition of the combustion mix and expansion and exhaust of the burnt combustion mix are produced by reciprocating pivoting movements of the individual pistons between two limit positions.
In the case of the oscillating-piston machine which is known from document WO 03/067033 A1, in the name of the same Applicant, four pistons are arranged in the housing, and these pistons revolve jointly about an axis of rotation which is arranged fixedly in the centre of the housing, and as they revolve they execute reciprocating pivoting movements about a pivot axis in the housing, with in each case two adjacent pistons pivoting in opposite directions. In this known oscillating-piston machine, in each case two pistons arranged diametrically opposite one another with respect to the centre of the housing are rigidly connected to one another to form a double piston, and two piston pairs of this type are in a crossed-over arrangement in the centre of the housing. In each case one working chamber is formed between in each case two end faces of the piston of the piston pairs facing one another, so that the known oscillating-piston machine has two working chambers. The size of the two working chambers which are arranged diametrically opposite with respect to the centre of the housing increases and decreases in the same direction with the reciprocating pivoting movement of the pistons.
The pistons of this known oscillating-piston machine are arranged in such a way in the housing that in their TDC position, in which the volumes of the two working chambers are at a minimum, they are positioned perpendicular to the axis of rotation. In this position, the centrifugal forces acting on the pistons during the revolution of the pistons about the axis of rotation are at a maximum. The result of this is that at high rotational speeds the expansion or movement of the pistons away from one another has to take place counter to the centrifugal forces, since the centrifugal forces counteract this movement of the pistons away from one another. In this oscillating-piston machine, the working chambers are always located outside and perpendicular to the axis of rotation.
The pistons of the known oscillating-piston machine are substantially in the form of a wedge of a sphere, and correspondingly so is the geometry of the working chambers.
Although the known oscillating-piston machine has very good operating properties, it is an object of the present invention to provide a new design of an oscillating-piston machine which differs from the design of the known oscillating-piston machine described above.